JP4498714B2 - Spray material - Google Patents

Description

  The present invention relates to a tunnel, such as a road, a railway, and a diversion channel, and a spray material used when spraying fast-setting concrete on an exposed natural ground surface on a slope, and shot concrete. It relates to the spraying method.

Conventionally, in order to prevent collapse of exposed ground in tunnel excavation work or the like, a method of spraying quick setting sprayed concrete in which powder quick setting agent is mixed with concrete is used (Patent Document 1, (See Patent Document 2 and Patent Document 3).
As the cement used in these spraying methods, ordinary Portland cement is frequently used in terms of rapid setting and initial strength development.
However, in recent years, the momentum for building a recycling-oriented society that recycles waste has increased, and the use of fine blast furnace slag powder has been recommended as part of the reduction of environmental impact, and even in mixed cement mixed with fine blast furnace slag powder. The development of materials with excellent quick setting and initial strength development has been awaited.

In addition, some areas have acidic geology. From the viewpoint of improving durability, it is desired to use blast furnace slag fine powder having excellent acid resistance in such areas.
However, blast furnace cement in which blast furnace slag fine powder and ordinary Portland cement are mixed has a problem in that the initial strength development at low temperatures is reduced.

And in order to avoid disasters caused by peeling caused by a decrease in initial strength, ensure a sufficient time to reach a sufficient safety strength even when it is applied by thin blowing or when it is blown thick. If the process could not proceed, the cost increase due to the prolonged construction period became a problem.
If it is possible to sufficiently bring out the ability of these quick hardening components with a specific quick setting agent, it is thought that the construction period can be shortened even in mixed cement using blast furnace slag fine powder with low hydration activity. .
Japanese Patent Publication No. 60-004149 JP 09-019910 A Japanese Patent Laid-Open No. 10-087358

  In view of the above situation, the present inventor can contribute to an environmental recycling society by using a mixed cement in which alumina cement and blast furnace slag fine powder are combined, and contains this mixed cement and calcium aluminate or gypsum. Thus, the present inventors have completed the present invention by obtaining the knowledge that a combination of the rapid setting agent and the rapid setting property and acid resistance can be obtained.

The present invention consists of (1) Blaine specific surface area of 2,500 cm ² / g or more alumina cement 35-50 parts and Blaine specific surface area of 3,000 cm ² / g or more blast furnace slag from 50 to 65 parts 100 parts of mixed cement , (2) in 100 parts of quick setting agent, (2-1) 30 to 70 parts of calcium aluminate having a brain value of 6,000 cm ² / g or more, and (2-2) a brain value of 5, 000 cm ² / g or more, containing 2 to 15 parts of quick setting agent containing 30 to 70 parts of acidic gypsum from weak alkali having a pH of 8 or less and (2-3) 5 to 20 parts of alkali metal aluminate. It is a spray material.

Hereinafter, the present invention will be described in detail.
In addition, the cement concrete as used in this invention is a general term for cement paste, mortar, and concrete.
Further, parts and% in the present invention are shown on a mass basis unless otherwise specified.

The alumina cement used in the present invention uses bauxite, high alumina, refined alumina, etc. as the alumina source, limestone, quicklime, etc. as the calcia source, and mainly contains CaO / Al ₂ O ₃ in the product. The clinker prepared by mixing into components and melted or fired in an electric furnace, radiation furnace, flat furnace, rotary kiln, etc. is pulverized by a pulverizer such as a tube mill, a vibration mill, a jet mill, and a roller mill. Commercially available alumina cement can also be used.
The particle size of the alumina cement is not particularly limited, but it is preferably 2,500 cm ² / g or more in terms of the specific surface area of the brain (hereinafter referred to as the brain value). If it is less than 2,500 cm ² / g, excellent quick setting may not be obtained.

Blast furnace slag fine powder used in the present invention (hereinafter referred to as slag powder) is a fine powder obtained by pulverizing or pulverizing and classifying molten slag produced as a by-product when producing pig iron from iron ore in a blast furnace, and aluminosilicate A fine powder mainly composed of a salt, and those defined in JIS A 6206 are preferable.
In the present invention, the slag powder contains CaO, SiO ₂ , Al ₂ O ₃ , MgO, etc., CaO / SiO ₂ is 1.15 to 1.25, (CaO + MgO) / (SiO ₂ + Al ₂ O ₃ ) is 0.90 to 1.05. Preferably, Al ₂ O ₃ is less than 15 parts and MgO is less than 5 parts. If it exceeds these ranges, excellent strength development may not be obtained.
The grain size of the slag powder is preferably 3,000 cm ² / g or more in terms of the brain value from the viewpoint of strength development.
The amount of slag powder used is preferably 15 to 65 parts, more preferably 20 to 50 parts, in a total of 100 parts of alumina cement and slag powder. If it is less than 15 parts, the contribution to the construction of a recycling society is small and the chlorine content in the cured product may not be reduced. If it exceeds 65 parts, the initial strength development at low temperatures may be impaired.

  The quick setting agent of the present invention contains at least calcium aluminate and gypsum.

The calcium aluminate used in the present invention is obtained by pulverizing a mixture of CaO raw material, Al ₂ O ₃ raw material, etc., firing in a kiln or heat treatment such as melting in an electric furnace. , 3CaO ・ Al ₂ O ₃ (C ₃ A), 12CaO ・ 7Al ₂ O ₃ (C ₁₂ A ₇ ), 11CaO ・ 7Al ₂ O ₃・ CaF ₂ (C ₁₁ A ₇ CaF ₂ ), 11CaO ・ 7Al ₂ O _{3 · CaCl 2 (C 11 a 7} CaCl 2), 2CaO · Al 2 O 3 · SiO 2 (C 2 aS), CaO · Al 2 O 3 (CA), and _{CaO · 2Al 2 O 3 (CA} 2) and the like It is shown and it is possible to use 1 type, or 2 or more types of these together.
Furthermore, it is possible to contain Mg or Si as a solution in which an alkali metal is dissolved or a mineralizer.
Calcium aluminate can be used either amorphous or crystalline, and these can be mixed.
It is not particularly limited particle size and its distribution of calcium aluminate, preferably 4,000 cm ² / g or more in Blaine value in terms of quick-setting property, 6,000 ² / g or more is more preferable. If it is less than 4,000 cm ² / g, excellent quick setting may not be obtained.
Although the usage-amount of a calcium aluminate is not specifically limited, 30-70 parts are preferable in 100 parts of quick setting agents. If it is less than 30 parts, excellent quick setting may not be obtained, and if it exceeds 70 parts, long-term strength development may be impaired.

Examples of the gypsum used in the present invention include hydrofluoric acid byproduct anhydrous gypsum and natural anhydrous gypsum anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum, and one or more of these can be used. .
The pH when the gypsum is immersed in water is preferably from a weak alkali having a pH of 8 or less to acidic. When the pH is high, the solubility of gypsum becomes high, which may inhibit the initial strength development. The pH here is a value obtained by measuring the pH of the diluted slurry at 20 ° C. with 1 g / 100 g of gypsum / ion exchange water using an ion exchange electrode or the like.
The particle size of the gypsum is preferably 3,000 cm ² / g or more in Blaine value, 5,000 cm ² / g or more is preferable in view of strength development.
Although the usage-amount of gypsum is not specifically limited, 30-70 parts are preferable in 100 parts of quick setting agents. If it is less than 30 parts, long-term strength development may be impaired, and if it exceeds 60 parts, excellent quick setting may not be obtained.

The alkali metal aluminate used in the present invention (hereinafter referred to as alkali aluminate) is obtained by mixing an alumina raw material and an alkali metal hydroxide. Examples of the alkali metal include lithium, sodium, and potassium. Etc.
The molar ratio of alkali aluminate R ₂ O to Al ₂ O ₃ is not particularly limited, but is preferably 0.65 to 1.2. If it is less than 0.65, excellent quick setting may not be obtained, and if it exceeds 1.2, long-term strength development may be impaired. Here, R is an alkali metal element.
The particle size of the alkali aluminate is preferably equal to or higher than that of calcium aluminate or gypsum from the viewpoint of improving quick setting.
The amount of alkali aluminate used is preferably 5 to 20 parts in 100 parts of the quick setting agent. If it is less than 5 parts, better quick setting may not be obtained, and if it exceeds 20 parts, quick setting may be impaired.

  In addition to these materials, the quick setting agent of the present invention can contain alkali metal carbonate, quicklime, slaked lime, aluminum hydroxide, and the like.

  Furthermore, in the present invention, addition of a pH adjuster, a dispersant, a stabilizer, an antifreeze agent, a water solubility promoter, an AE agent, a water reducing agent, an AE water reducing agent, a set retarder, a thickener, a fiber, a fine powder, and the like An agent can be used in combination as long as the object of the present invention is not substantially inhibited.

  The amount of the rapid setting agent is preferably 2 to 15 parts with respect to 100 parts of the mixed cement of alumina cement and slag powder. If it is less than 2 parts, the excellent setting properties may not be exhibited, and if it exceeds 15 parts, long-term strength development may be deteriorated.

The amount of mixed cement used in the shotcrete is preferably 330 to 500 kg / m ³ , and the water cement ratio is preferably 40 to 65%. Outside this range, problems may arise in workability and durability.
Moreover, it does not specifically limit regarding the slump and flow value of spray cement concrete.

As this spraying method, a commonly used wet spraying method or a dry spraying method can be used.
Examples of the wet spraying method include a method of mixing a quick setting agent in the sprayed cement concrete, and the dry spraying method includes adding water and a quick setting agent to cement, sand, and gravel concrete compositions. And a method of mixing water with cement, sand, gravel, and quick-setting agent.

  As a method of mixing the quick setting agent with the sprayed cement concrete, it is preferable to mix it immediately before spraying using a Y-shaped tube or the like. Specifically, quick setting agent is added to sprayed cement concrete that has been pumped to prepare quick setting spray cement concrete, and the time until the quick setting spray cement concrete is discharged is 10 times. It is preferably within 2 seconds, more preferably within 2 seconds.

Further, the quick setting sprayed cement concrete of the present invention can be sprayed directly on a slope ground, or on a place where a frame skeleton is arranged, in addition to a ground ground of a tunnel.
Here, the frame skeleton is a structure in which a wire mesh, a reinforcing bar, a steel frame, and the like are combined and fixed to a wall surface, and rapidly setting sprayed cement concrete is sprayed on the frame skeleton to form a reinforcing steel-containing concrete frame.

  By using the spray material of the present invention, spray cement concrete, and the spray method using the same, it is possible to impart high quick setting properties even when using industrial slag powder, It has effects such as having acid resistance.

  Hereinafter, the present invention will be described in more detail based on experimental examples.

  Using a mortar with a cement / sand ratio (C / S) of 1/3 and a water / cement ratio (W / C) of 60%, using 60 parts of alumina cement and 40 parts of slag powder, this mixed cement 100 The part penetration resistance value was measured using 8 parts of the quick setting agent of the type shown in Table 1. The test environment temperature is 20 ° C. The results are also shown in Table 1.

<Materials used>
Alumina cement: Commercially available slag powder: manufactured by Nippon Steel Blast Furnace Co., Ltd., trade name Sment, brain value 4,000cm ² / g
Calcium aluminate: C ₁₂ A ₇ composition, amorphous, brain value 8,000cm ² / g
Gypsum: anhydrous gypsum, first grade reagent, brain value 6,000cm ² / g
Alkali aluminate: sodium aluminate, first grade reagent, brain value 4,000cm ² / g
Water: tap water sand: river sand from Himekawa, Niigata Prefecture, specific gravity 2.62

<Measurement method>
Proctor penetration resistance value: Confirmation of setting properties, compliant with ASTM C 403 “Concrete setting time test method by penetration resistance”. After mixing mortar and quick setting agent, evaluate the setting properties for 1 minute and 3 minutes.

Except for using the quick-setting agent used in Experiment No. 1-9, using the amount of alumina cement and slag powder shown in Table 2, and measuring the Procter penetration resistance and weight change rate, The same test was performed.
For comparison, the same test was performed when ordinary Portland cement was used. The results are also shown in Table 2.

<Materials used>
Ordinary Portland cement: Commercial product

<Measurement method>
Weight change rate: Acid resistance test, the cured body was cured in water for 28 days, then immersed in a 5% strength aqueous sulfuric acid solution for 28 days, and the change in weight before and after immersion was measured.

Claims (1)

(1) Blaine specific surface area of 2,500 cm ² / g or more alumina cement 35-50 parts and Blaine specific surface area of 3,000 cm ² / g or more blast furnace slag 50 consists of 65 parts of mixed cement 100 parts (2) In 100 parts of the quick setting agent, (2-1) 30 to 70 parts of calcium aluminate having a brain value of 6,000 cm ² / g or more and (2-2) a brain value of 5,000 cm ² / g above, and the spray formed by the pH8 following weakly alkaline with 30 to 70 parts plaster of acidic (2-3) rapid setting agent containing 5 to 20 parts of an alkali metal aluminate containing 2 to 15 parts Wood.